In the present patent application, the term base station should be understood as a general term covering various types thereof, depending on the network at which the respective base station is operative. For example, 4G networks comprise e-nodes B (eNB), 3G network comprise nodesB, 2G networks such as WiMAX networks comprise BTS, etc.
FIG. 1 (prior art) illustrates a cellular network comprising service gateways (GWs or SGWs) communicating with base stations (such as e-nodesB marked eNB) via a Transport Network (“TN”) which assists in establishing communication links between the GWs and the base stations. For communication to be carried out between base stations (eNBs), FIG. 1 illustrates a modern network interface known as X2, associated with the Transport Network TN and adapted to connect base stations in a full mesh type of connection, thereby enabling direct communications between the elements (enBs) of the cellular network and consequently decreasing or eliminating all together the need to funnel data back and forth through service gateways SGWs. The X2 interface is a logical network element, usually formed for 4G networks in the TN (thus referred to as a cellular backhauling network) provisioned to interconnect the base stations and the gateways. The main advantages of the full mesh X2 interface are direct connectivity between adjacent eNBs and smooth handover there-between.
For communications with GWs, the base stations use so-called S1 interface connections via the same cellular backhauling network.
In modern networks, the number of enodesB (eNBs, which may be, for example, picocell or femtocell nodes) is permanently increased, and in future the number of eNBs may be increased by factor of up to 100 and even 1000. In such cases, in many real transport network implementations, the full mesh connectivity provided in the backhauling network between eNBs would become very expensive from the point of logical connections and resources required to support full mesh coverage.
FIG. 2 (prior art) illustrates a schematic top view of a plurality of network elements NEs being part of an optical fiber Transport Network. In this schematic illustration, an exemplary NE is interconnected with base stations of a cellular network. CMS of the cellular network are not shown in this Figure. The fiber transport network TN of FIG. 2 has a topology comprising a core ring network and a number of sub-networks or domains 10, 12, 14 which may be referred to as “access” domains. Each of these access domains comprises a number of ring networks (for example, fiber ring networks) of network elements (NEs, PEs), and together with other network elements of the TN, interconnect base stations of the cellular network. It is quite a common situation that direct connections are required between some nodes B and different ring networks or even different domains, but such connections cannot be reached without having full mesh connectivity in the TN. The full mesh approach turns to be too expensive due to the number of base stations, due to their long distance from one another, etc. In our example, each fiber ring consists of 4 NE or PE (Network Element or Provider Edge) elements/cards.
In FIG. 2, there are 3 “access” rings per “access network domain”, and there are 3 such domains. In total, we have 4×3×3=36 NEs. Every NE should be provided with the appropriate connectivity. For each one of the N elements of the TN (backhauling network), N-1 connectivities (PWs) are required. If MPLS tunnels are counted, for the full MESH configuration, 36*(36-1) bidirectional tunnels are required. Then, pseudo wires (PWs) should be considered for each NE: for a full mesh topology, 35 PWs will be required.
According to the typical practice today, a cellular backhauling Transport Network (TN) provides two main types of connectivity for Cellular backhauling. E-tree connectivity is provided for point-to-multipoint services, while ELAN connectivity is provided for multipoint-to-multipoint services. Usually, in order to provide interconnection between eNBs and GWs, mapping of the E-tree connectivity is performed. To provide interconnection between eNBs, mapping of E-LAN (full mesh, mp-t-mp) connectivity is typically performed. Usually, these operations are performed per specific cellular network/operator (i.e., for those NEs of the TN, which serve base stations and GWs of that specific cellular operator.
US2011098046 A describes methods and an apparatus for performing a cell selection, by a multi-mode terminal, from a legacy network (2G, 3G) to an advanced network (4G). The terminal performs the cell selection upon the existence of a Base Station (BS) on the advanced network system. However, it only relates to the nodesB section of the network and does not relate to solving the problem in the transport network.